PIC16F72SLASHML datasheet(55/136 Pages) MICROCHIP

55 / 136 page

 2002 Microchip Technology Inc.

DS39597B-page 53

PIC16F72

10.0

ANALOG-TO-DIGITAL

CONVERTER (A/D) MODULE

The analog-to-digital (A/D) converter module has five

inputs for the PIC16F72.

The A/D allows conversion of an analog input signal to

a corresponding 8-bit digital number. The output of the

sample and hold is the input into the converter, which

generates the result via successive approximation. The

analog reference voltage is software selectable to

either the device’s positive supply voltage (VDD) or the

voltage level on the RA3/AN3/VREF pin.

The A/D converter has a unique feature of being able

to operate while the device is in SLEEP mode. To oper-

ate in SLEEP, the A/D conversion clock must be

derived from the A/D’s internal RC oscillator.

The A/D module has three registers:

• A/D Result Register

ADRES

• A/D Control Register 0

ADCON0

• A/D Control Register 1

ADCON1

A device RESET forces all registers to their RESET

state. This forces the A/D module to be turned off and

any conversion is aborted.

The ADCON0 register, shown in Register 10-1, con-

trols the operation of the A/D module. The ADCON1

tions of the port pins. The port pins can be configured

as analog inputs (RA3 can also be a voltage reference)

or a digital I/O.

For more information on use of the A/D Converter, see

AN546 - Use of A/D Converter, or refer to the

PICmicro™

Mid-Range

MCU

Family

Reference

Manual (DS33023).

ADCON0: A/D CONTROL REGISTER 0 (ADDRESS 1Fh)

R/W-0

U-0

R/W-0

ADCS1

ADCS0

CHS2

CHS1

CHS0

GO/DONE

—

ADON

bit 7

bit 0

bit 7-6

ADCS<1:0>: A/D Conversion Clock Select bits

=FOSC/2

=FOSC/8

=FOSC/32

=FRC (clock derived from the internal A/D module RC oscillator)

bit 5-3

CHS<2:0>: Analog Channel Select bits

000

= Channel 0, (RA0/AN0)

001

= Channel 1, (RA1/AN1)

010

= Channel 2, (RA2/AN2)

011

= Channel 3, (RA3/AN3)

100

= Channel 4, (RA5/AN4)

bit 2

GO/DONE: A/D Conversion Status bit

If ADON = 1:

= A/D conversion in progress (setting this bit starts the A/D conversion)

= A/D conversion not in progress (this bit is automatically cleared by hardware when the A/D

conversion is complete)

bit 1

Unimplemented: Read as ‘0’

bit 0

ADON: A/D On bit

= A/D converter module is operating

= A/D converter module is shut-off and consumes no operating current

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

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